Setup:

Prerequisites

Android

iOS

Unity 5.0 or later

Xcode 8.0 or later

If you don't have a Unity project already, you can download one of our
quickstart samples and experiment with a specific Firebase feature.
If you're using a quickstart, remember to get the bundle identifier from the
project settings; you need it for the next step.

Set up your app in the Firebase console

To add Firebase to your app, you need a Firebase project and a Firebase
configuration file for your app.

To create a Firebase project:

Create a Firebase project in the Firebase console, if you don't already
have one. Click Add project. If you already have an existing Google
project associated with your mobile app, select it from the Project name
drop down menu. Otherwise, enter a project name to create a new project.

Optional: Edit your Project ID. Your project is given a unique ID
automatically, and it's used in publicly visible Firebase features such as
database URLs and your Firebase Hosting subdomain. You can change it now
if you want to use a specific subdomain.

Follow the remaining setup steps and click Create project (or
Add Firebase if you're using an existing project) to begin provisioning
resources for your project. This typically takes a few minutes. When the
process completes, you'll be taken to the project overview.

Android

Click Add Firebase to your Android app and follow the setup steps. If
you're importing an existing Google project, this may happen automatically
and you can just
download the config file.

When prompted, enter your app's package name. It's important to enter the
package name your app is using; this can only be set when you add an app to
your Firebase project.

During the process, you'll download a google-services.json file. You
can
download this file
again at any time.

After you add the initialization code, run your app to send verification to
the Firebase console that you've successfully installed Firebase.

iOS

Click Add Firebase to your iOS app and follow the setup steps. If you're
importing an existing Google project, this may happen automatically and you
can just
download the config file.

When prompted, enter your app's bundle ID. It's important to enter the
bundle ID your app is using; this can only be set when you add an app to
your Firebase project.

During the process, you'll download a GoogleService-Info.plist file. You
can
download this file
again at any time.

After you add the initialization code, run your app to send verification to
the Firebase console that you've successfully installed Firebase.

Drag the GoogleService-Info.plist downloaded from the Firebase console
into any folder in the Unity project.

Note: If you have multiple build variants with different bundle IDs defined,
each app must be added to your project in Firebase console.

Initialize the SDK

The Firebase Unity SDK on Android requires
Google Play services,
which must be up-to-date before the SDK can be used. The following code should
be added at the start of your application to check for and optionally update
Google Play services to the version required by the Firebase Unity SDK before
calling any other methods in the SDK.

Next Steps

After a user signs in for the first time, a new user account is created and
linked to the credentials—that is, the user name and password, phone
number, or auth provider information—the user signed in with. This new
account is stored as part of your Firebase project, and can be used to identify
a user across every app in your project, regardless of how the user signs in.